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[snappyHexMesh] Problem airfoil snappyhexmesh add layer

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Old   April 18, 2017, 04:25
Default Problem airfoil snappyhexmesh add layer
  #1
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/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 4.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object snappyHexMeshDict;
}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Which of the steps to run
castellatedMesh true;
snap true;
addLayers true;


// Geometry. Definition of all surfaces. All surfaces are of class
// searchableSurface.
// Surfaces are used
// - to specify refinement for any mesh cell intersecting it
// - to specify refinement for any mesh cell inside/outside/near
// - to 'snap' the mesh boundary to the surface
geometry
{
/*
moving.stl
{
type triSurfaceMesh;
name moving_2nd;
regions
{


"interface1" { name "interface1";}
"interface2" { name "interface2";}
"interface3" { name "interface3";}

}
}
*/
upper_airfoil.stl
{
type triSurfaceMesh;
name upper_airfoil;
/*
regions
{

upper_airfoil
{ name upper_airfoil;}

}

*/
}



bottom_airfoil.stl
{
type triSurfaceMesh;
name bottom_airfoil;
/*
regions
{

bottom_airfoil
{ name bottom_airfoil;}


}
*/
}
/*
cylinder.stl
{
type triSurfaceMesh;
name cylinder;

}
*/
AMI.stl
{
type triSurfaceMesh;
name AMI;
/*
regions
{

"AMI"
{ name "AMI";}


}
*/
}
/*
box
{

type searchableBox;
min (-2.5 -2.5 3);
max (2.5 2.5 7);

}
*/


};



// Settings for the castellatedMesh generation.
castellatedMeshControls
{

// Refinement parameters
// ~~~~~~~~~~~~~~~~~~~~~

// If local number of cells is >= maxLocalCells on any processor
// switches from from refinement followed by balancing
// (current method) to (weighted) balancing before refinement.
maxLocalCells 100000;

// Overall cell limit (approximately). Refinement will stop immediately
// upon reaching this number so a refinement level might not complete.
// Note that this is the number of cells before removing the part which
// is not 'visible' from the keepPoint. The final number of cells might
// actually be a lot less.
maxGlobalCells 2500000;

// The surface refinement loop might spend lots of iterations refining just a
// few cells. This setting will cause refinement to stop if <= minimumRefine
// are selected for refinement. Note: it will at least do one iteration
// (unless the number of cells to refine is 0)
minRefinementCells 10;
// Allow a certain level of imbalance during refining
// (since balancing is quite expensive)
// Expressed as fraction of perfect balance (= overall number of cells /
// nProcs). 0=balance always.
maxLoadUnbalance 0.10;
// Number of buffer layers between different levels.
// 1 means normal 2:1 refinement restriction, larger means slower
// refinement.
nCellsBetweenLevels 3;



// Explicit feature edge refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Specifies a level for any cell intersected by its edges.
// This is a featureEdgeMesh, read from constant/triSurface for now.

features
(

{
file "AMI.extendedFeatureEdgeMesh";
level 6;
}


{
file "upper_airfoil.extendedFeatureEdgeMesh";
level 6;
}

{
file "bottom_airfoil.extendedFeatureEdgeMesh";
level 6;
}





);



// Surface based refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~

// Specifies two levels for every surface. The first is the minimum level,
// every cell intersecting a surface gets refined up to the minimum level.
// The second level is the maximum level. Cells that 'see' multiple
// intersections where the intersections make an
// angle > resolveFeatureAngle get refined up to the maximum level.

refinementSurfaces
{


upper_airfoil
{
level (6 8);

patchInfo
{
type patch;

}

}

bottom_airfoil
{
level (6 8);

patchInfo
{
type patch;
}

}

/*
cylinder
{
// Surface-wise min and max refinement level
level (1 1);

//faceZone cylinder;
cellZone cylinder;
cellZoneInside inside;

//bounadry internal;
}
*/
AMI
{
level (6 6);

faceZone AMI;
faceType baffle;
cellZone cylinder;
cellZoneInside inside;


}


}
/*

moving_2nd
{
// Surface-wise min and max refinement level
level (1 1);

faceZone moving_2;
cellZone moving_2;
//cellZoneInside inside;

//bounadry internal;

regions
{

"interface1" { level (1 1); patchInfo { type patch;}}
"interface2" { level (1 1); patchInfo { type patch;}}
"interface3" { level (1 1); patchInfo { type patch;}}


}



}





}
*/


resolveFeatureAngle 30;


// Region-wise refinement
// ~~~~~~~~~~~~~~~~~~~~~~

// Specifies refinement level for cells in relation to a surface. One of
// three modes
// - distance. 'levels' specifies per distance to the surface the
// wanted refinement level. The distances need to be specified in
// descending order.
// - inside. 'levels' is only one entry and only the level is used. All
// cells inside the surface get refined up to the level. The surface
// needs to be closed for this to be possible.
// - outside. Same but cells outside.

refinementRegions
{
/*
box
{
mode inside;
levels ((1e15 2));

}
*/
}

// Mesh selection
// ~~~~~~~~~~~~~~

// After refinement patches get added for all refinementSurfaces and
// all cells intersecting the surfaces get put into these patches. The
// section reachable from the locationInMesh is kept.
// NOTE: This point should never be on a face, always inside a cell, even
// after refinement.
// This is an outside point locationInMesh (-0.033 -0.033 0.0033);
locationInMesh (-4 0.1 1); // Inside point

// Whether any faceZones (as specified in the refinementSurfaces)
// are only on the boundary of corresponding cellZones or also allow
// free-standing zone faces. Not used if there are no faceZones.
allowFreeStandingZoneFaces true;
}



// Settings for the snapping.
snapControls
{
//- Number of patch smoothing iterations before finding correspondence
// to surface
nSmoothPatch 3;

//- Relative distance for points to be attracted by surface feature point
// or edge. True distance is this factor times local
// maximum edge length.
tolerance 2.0;

//- Number of mesh displacement relaxation iterations.
nSolveIter 300;

//- Maximum number of snapping relaxation iterations. Should stop
// before upon reaching a correct mesh.
nRelaxIter 5;//5;

// Feature snapping

//- Number of feature edge snapping iterations.
// Leave out altogether to disable.
nFeatureSnapIter 10;

//- Detect (geometric) features by sampling the surface
implicitFeatureSnap false;

//- Use castellatedMeshControls::features
explicitFeatureSnap true;

//- Detect features between multiple surfaces
// (only for explicitFeatureSnap, default = false)
multiRegionFeatureSnap false;
}



// Settings for the layer addition.
addLayersControls
{
// Are the thickness parameters below relative to the undistorted
// size of the refined cell outside layer (true) or absolute sizes (false).
relativeSizes true;

// Per final patch (so not geometry!) the layer information
layers
{
"upper_airfoil"
{
nSurfaceLayers 10;
}

"bottom_airfoil"
{
nSurfaceLayers 10;
}

}

// Expansion factor for layer mesh
expansionRatio 1;


// Wanted thickness of final added cell layer. If multiple layers
// is the thickness of the layer furthest away from the wall.
// Relative to undistorted size of cell outside layer.
// See relativeSizes parameter.
finalLayerThickness 0.007;

// Minimum thickness of cell layer. If for any reason layer
// cannot be above minThickness do not add layer.
// See relativeSizes parameter.
minThickness 0.0007;

// If points get not extruded do nGrow layers of connected faces that are
// also not grown. This helps convergence of the layer addition process
// close to features.
nGrow 0;


// Advanced settings

// When not to extrude surface. 0 is flat surface, 90 is when two faces
// are perpendicular
featureAngle 60;

// At non-patched sides allow mesh to slip if extrusion direction makes
// angle larger than slipFeatureAngle.
slipFeatureAngle 30;

// Maximum number of snapping relaxation iterations. Should stop
// before upon reaching a correct mesh.
nRelaxIter 5;

// Number of smoothing iterations of surface normals
nSmoothSurfaceNormals 1;

// Number of smoothing iterations of interior mesh movement direction
nSmoothNormals 3;

// Smooth layer thickness over surface patches
nSmoothThickness 10;

// Stop layer growth on highly warped cells
maxFaceThicknessRatio 0.5;

// Reduce layer growth where ratio thickness to medial
// distance is large
maxThicknessToMedialRatio 0.3;

// Angle used to pick up medial axis points
minMedianAxisAngle 90;

// Create buffer region for new layer terminations
nBufferCellsNoExtrude 0;


// Overall max number of layer addition iterations. The mesher will exit
// if it reaches this number of iterations; possibly with an illegal
// mesh.
nLayerIter 50;


// Max number of iterations after which relaxed meshQuality controls
// get used. Up to nRelaxIter it uses the settings in meshQualityControls,
// after nRelaxIter it uses the values in meshQualityControls::relaxed.
nRelaxedIter 20;
}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
#include "meshQualityDict"

// Optional : some meshing phases allow usage of relaxed rules.
// See e.g. addLayersControls::nRelaxedIter.
relaxed
{
//- Maximum non-orthogonality allowed. Set to 180 to disable.
maxNonOrtho 70;
}

// Advanced

//- Number of error distribution iterations
nSmoothScale 4;
//- Amount to scale back displacement at error points
errorReduction 0.75;
}


// Advanced

// Write flags
writeFlags
(
scalarLevels // write volScalarField with cellLevel for postprocessing
layerSets // write cellSets, faceSets of faces in layer
layerFields // write volScalarField for layer coverage
);


// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1E-6;


// ************************************************** *********************** //





this is my snappyhexmesh.. i don't know why layer doesn't generate...
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File Type: jpg ????_snappy_airfoil.jpg (175.1 KB, 163 views)
bye bye my blue is offline   Reply With Quote

Old   May 5, 2017, 06:56
Default Check your blockmesh
  #2
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Join Date: Oct 2015
Posts: 1
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YEberhard is on a distinguished road
Hey Hey bye bye my blue,

the first problem seems to be in the blockMesh.
SnappyHexMesh dosn't like high aspect ratios in the backgroundmesh.
Try a cell edge ratio close to 1

the second thing change some layer parameter

E.g.
expansionRatio 1.25;
finalLayerThickness 0.3;
minThickness 0.0001;

KR
Yannick
YEberhard is offline   Reply With Quote

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